U.S. patent application number 13/825804 was filed with the patent office on 2013-11-07 for channel access systems and methods for cognitive relaying for cellular systems.
This patent application is currently assigned to INTERDIGITAL PATENT HOLDINGS, INC.. The applicant listed for this patent is Erdem Bala, Tao Deng, Samian J. Kaur, Feilu Liu, Rui Yang. Invention is credited to Erdem Bala, Tao Deng, Samian J. Kaur, Feilu Liu, Rui Yang.
Application Number | 20130294356 13/825804 |
Document ID | / |
Family ID | 44764220 |
Filed Date | 2013-11-07 |
United States Patent
Application |
20130294356 |
Kind Code |
A1 |
Bala; Erdem ; et
al. |
November 7, 2013 |
CHANNEL ACCESS SYSTEMS AND METHODS FOR COGNITIVE RELAYING FOR
CELLULAR SYSTEMS
Abstract
Embodiments contemplate channel access systems and methods for
cognitive relaying in unlicensed and lightly licensed bands.
Embodiments contemplate managing nodes of a wireless network
operating in an unlicensed and or lightly licensed band. One or
more embodiments may include sensing an idle channel in the
unlicensed and/or lightly licensed band. Further, embodiments
contemplate using the idle channel for wireless communication.
Inventors: |
Bala; Erdem; (Farmingdale,
NY) ; Kaur; Samian J.; (Plymouth Meeting, PA)
; Liu; Feilu; (San Diego, CA) ; Yang; Rui;
(Greenlawn, NY) ; Deng; Tao; (Roslyn, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Bala; Erdem
Kaur; Samian J.
Liu; Feilu
Yang; Rui
Deng; Tao |
Farmingdale
Plymouth Meeting
San Diego
Greenlawn
Roslyn |
NY
PA
CA
NY
NY |
US
US
US
US
US |
|
|
Assignee: |
INTERDIGITAL PATENT HOLDINGS,
INC.
Wilmington
DE
|
Family ID: |
44764220 |
Appl. No.: |
13/825804 |
Filed: |
September 22, 2011 |
PCT Filed: |
September 22, 2011 |
PCT NO: |
PCT/US2011/052843 |
371 Date: |
July 30, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61385741 |
Sep 23, 2010 |
|
|
|
Current U.S.
Class: |
370/329 |
Current CPC
Class: |
H04W 88/06 20130101;
H04W 72/0453 20130101; H04W 56/001 20130101; H04W 74/0808 20130101;
H04B 7/15542 20130101; H04W 88/04 20130101; H04W 16/14 20130101;
H04W 72/02 20130101; H04B 7/2606 20130101 |
Class at
Publication: |
370/329 |
International
Class: |
H04W 72/04 20060101
H04W072/04 |
Claims
1-20. (canceled)
21. A first device, comprising: a processor configured, at least in
part, to: determine a respective plurality of access opportunities
for a respective plurality of second devices, the respective access
opportunities providing the respective plurality of second devices
with coordinated access to a first channel in a first frequency
band; and initiate the transmission of the respective plurality of
access opportunities to the respective plurality of second devices
via a second channel in a second band.
22. The first device of claim 21, wherein the first frequency band
is at least one of an unlicensed band or a lightly-licensed band,
and the second frequency band is a licensed band.
23. The first device of claim 21, wherein the first device is a
cognitive relay node.
24. The first device of claim 21, wherein the respective plurality
of second devices are a respective plurality of wireless
transmit/receive units (WTRUs).
25. The first device of claim 24, wherein the coordinated access to
the first channel in the first frequency band provides for
non-overlapping-in-time access of the respective plurality of WTRUs
to the first channel in the first frequency band.
26. A method, comprising: determining, by a device, a respective
plurality of access opportunities for a respective plurality of
wireless transmit/receive units (WTRUs), the respective access
opportunities providing the respective plurality of WTRUs with
coordinated access to a first channel in a first frequency band;
and transmitting, by the device, the respective plurality of access
opportunities to the respective plurality of WTRUs as a part of
control information via a control channel in a second band.
27. The method of claim 26, further comprising: obtaining, by the
respective plurality of WTRUs, the respective plurality of access
opportunities by decoding the control channel.
28. The method of claim 26, further comprising: obtaining, by the
respective plurality of WTRUs, one or more properties of an
incoming transmission on the first channel of the first frequency
band by decoding the control channel.
29. The method of claim 26, further comprising: transmitting, by
the respective plurality of WTRUs, a respective response to the
control information via a second channel in the second band.
30. The method of claim 26, wherein the device is a cognitive relay
node, the first frequency band is at least one of an unlicensed
band or a lightly-licensed band, and the second frequency band is a
licensed band.
31. The method of claim 26, wherein each of the respective
plurality of WTRUs have a respective sensing region.
32. The method of claim 31, wherein each of the respective
plurality of WTRUs is within the respective sensing region of at
least one other WTRU of the respective plurality of WTRUs.
33. The method of claim 32, further comprising: conducting, by each
of the respective plurality of WTRUs, at least one of a fixed-time
sensing or a variable time-sensing for transmissions from at least
one other WTRU of the respective plurality of WTRUs.
34. The method of claim 33, further comprising: conducting, by each
of the respective plurality of WTRUs, the fixed-time sensing by
performing a measurement of at least one of a transmission duration
or an attempt interval.
35. The method of claim 26, further comprising: measuring, by at
least one WTRU of the respective plurality of WTRUs, a utilization
rate of the first channel in the first frequency band.
36. The method of claim 35, further comprising: coordinating, by
the at least one WTRU of the respective plurality of WTRUs, at
least one transmission based on the utilization rate, the at least
one transmission being via the first channel in the first frequency
band to at least one other WTRU of the respective plurality of
WTRUs.
37. A device, comprising: a processor configured, at least in part,
to: determine a respective plurality of access opportunities for a
respective plurality of wireless transmit/receive units (WTRUs),
the respective access opportunities providing the respective
plurality of WTRUs with transmission access to respective channels
in a first frequency band; and initiate the transmission of the
respective plurality of access opportunities to the respective
plurality of WTRUs via a second channel in a second band.
38. The device of claim 37, wherein the processor is further
configured to monitor at least one of a transmission queue length
or a buffer status report of at least one WTRU of the plurality of
WTRUs.
39. The device of claim 38, wherein the processor is further
configured to determine a bandwidth for the at least one WTRU of
the plurality of WTRUs based, at least in part, on the at least one
of the transmission queue length or the buffer status report.
40. The device of claim 37, wherein the device is a cognitive relay
node, the first frequency band is at least one of an unlicensed
band or a lightly-licensed band, and the second frequency band is a
licensed band.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Patent Application No. 61/385,741, titled "Channel Access Systems
and Methods for Cognitive Relaying in Unlicensed Bands", filed on
Sep. 23, 2010, the content of which being hereby incorporated by
reference herein, for all purposes.
BACKGROUND
[0002] Spectrum may be available for communication nodes and
operators of such nodes in both unlicensed bands and lightly
licensed bands. The Federal Communications Commission (FCC)
conceived the license-exempt bands (e.g., unlicensed bands) to
provide a portion of public access spectrum at no licensed
cost.
[0003] The FCC has also established the lightly licensed bands in
which licensees may pay a small fee for a nationwide, non-exclusive
license for certain public access spectrum. Those that take such
licenses may then pay an additional nominal fee for each node that
may deployed. Such client nodes may be fixed or mobile. Neither the
nodes nor their operators may require an additional license.
SUMMARY
[0004] This Summary is provided to introduce a selection of
concepts in a simplified form that are further described below in
the Detailed Description of Illustrative Embodiments. This Summary
is not intended to identify key features or essential features of
the claimed subject matter, nor is it intended to be used to limit
the scope of the claimed subject matter.
[0005] Embodiments contemplate options for use of unlicensed or
lightly licensed spectrum by cellular systems. For example,
embodiments contemplate the use of the Physical layer (PHY) and/or
Medium Access Control (MAC) layer of a legacy system operating in
the unlicensed spectrum (such as a 802.11 based system, for
example) and fragment/combine the transmitted/received traffic on
the licensed and unlicensed band above the PHY/MAC layers. Also by
way of example, embodiments contemplate the design of a specific
PHY and/or MAC layers for the unlicensed spectrum based on
respective cellular standards (for example LTE) and change the
higher layers to fragment/combine the traffic.
[0006] The design of a specific PHY and/or MAC layers may provide
for a number of capabilities or features he. For example,
embodiments recognize that: [0007] 802.11 technologies may operate
only in certain bands while the total amount of unlicensed or
lightly licensed spectrum is much larger. Therefore 802.11
technologies approach may result in spectrum restrictions. [0008]
The spectral efficiency of LTE may be much higher than other
standardized technologies that are designed for devices operating
in the unlicensed band. The advanced features in PHY and MAC in LTE
may not exist in some 802.11 technologies. Also, the PHY layers may
not be totally compatible. For example, the cyclic prefix and OFDM
symbol lengths of 802.11 are much smaller than those of LTE. This
may restrict the use of 802.11 technologies to environments where
delay spread may be much smaller than those in cellular
environments. [0009] 802.11 may aim to design an ad hoc network and
therefore may use certain protocols to minimize collision where
these protocols are distributed, for example carrier sense multiple
access with collision avoidance (CSMA/CA). Although there may be a
need to use similar approaches for coexistence purposes, a tighter
coordination among the cellular nodes (for example managed by the
cognitive transmitter such as the relay node) may be used to design
more efficient medium access protocols. [0010] Embodiments
recognize that several networks may exist simultaneously in the
same spectrum. The spectrum could be unlicensed or lightly
licensed; or could be licensed where the operator leases it to
cognitive users. One or more embodiments contemplate techniques
that may manage coexistence among cellular and other users may be
applicable to a wider range of problems/scenarios. [0011] WiFi
offloading may be used because operators may want to take the
advantage of using the unlicensed spectrum while they may not have
full control over the WiFi communications. If a cellular standard
supports communications over licensed and unlicensed bands, full
control over the transmission may improve the efficiency (for
example by using intelligent relaying schemes which will utilize
the licensed and unlicensed spectrum in an optimal way under the
same controller).
[0012] Embodiments recognize that multi-tier heterogeneous
networks, where secondary nodes may create smaller cells overlaid
on the cellular cell, are supported in LTE-A and other standards.
The secondary cells may re-use the cellular spectrum with the
primary network and enhance spectral efficiency. Because of the
spectrum sharing property, embodiments contemplate that
interference may need to be addressed with intelligent interference
management techniques. Embodiments recognize schemes that may
concentrate on resource orthogonalization between the primary and
secondary networks. Embodiments contemplate cognitive cooperation
that may improve system performance by applying appropriate
interference management techniques, efficient utilization of the
spectrum, and/or cooperation between the primary and secondary
nodes. In current cellular standards, the bandwidth has grown
significantly; up to 100 MHz for downlink and uplink in LTE-A.
Efficient utilization of this spectrum and spectrum in bands other
than the cellular band (for example other licensed bands and/or
unlicensed bands) is contemplate by one or more embodiments.
[0013] Embodiments recognize methods that may enable cognitive
nodes to use the resources of primary systems such as cellular
systems, television transmission systems, etc., for example.
Embodiments contemplate that cognitive radio techniques may also be
used to improve the performance of cellular systems. In one or more
embodiments, some nodes of the primary system, which for example
may be the cellular system, may have cognitive radio capabilities.
Relays and other low power transmission nodes such as picocells,
femto cells, may have certain cognitive radio capabilities. Also,
in one or more embodiments, the traditional cellular model may be
extended to include direct communications between the wireless
transmit/receive units (WTRUs, which may be referred to as User
Equipment (UE). WTRUs could work as helpers to traditional cellular
connections to facilitate improved spectral efficiency, coverage,
and/or energy efficiency. The helper WTRUs may be intermediate
nodes that help deliver data to and from the end-user WTRU. The
helper WTRU could work as a simple relay or a cooperative relay,
for example. Embodiments contemplate techniques that may be enable
use of the new spectrum in the crosslink, between the WTRUs in both
directions.
[0014] For simplicity, in the rest of the present disclosure, the
term "relay node" may be used to refer to either an infrastructure
relay or a helper WTRU. Cognitive relays may improve the system
performance by relaying the data of the primary users by
dynamically accessing under-utilized spectrum. As opposed to the
traditional relays, embodiments contemplate that cognitive relays
may also have their own data to be transmitted to the cognitive
receivers.
[0015] Embodiments contemplate channel access systems and methods
for cognitive relaying in unlicensed bands. Particularly, the one
or more embodiments may provide systems and methods to enable
access to the unlicensed (and lightly licensed) spectrum by
cellular nodes. The communications over the licensed and unlicensed
bands may be between a central node (such as an infrastructure
relay, picocell, base station, etc.) and mobile terminals or
between mobile terminals.
[0016] Embodiments contemplate that cognitive radios may utilize
radio and signal processing technologies to support new wireless
users (cognitive or secondary users) in the existing spectrum
without degrading the performance of incumbent users (e.g., primary
users). These radios may use intelligent spectrum allocation
policies to support the new users while using novel interference
management and cooperation techniques. Embodiments recognize that
Bluetooth and 802.11 operating in unlicensed bands may need to obey
rules such as maximum transmit power and a shared channel access
mechanism. Embodiments contemplate that cognitive users may operate
both in licensed and unlicensed bands but use advanced technology
so that minimal impact may be made to the non-cognitive users.
[0017] Embodiments contemplate techniques and methods for cognitive
relaying in the next generation cellular systems. Embodiments
contemplate the coexistence of networks in the same spectrum. These
networks could be of different types, for example cellular systems
and ad hoc networks in unlicensed spectrum. Or, these networks may
include cognitive nodes using the cellular spectrum; or of the same
type, for example cellular systems of different operators.
Embodiments contemplate techniques that may control interference
and manage sharing of the spectrum. The contemplated techniques may
be designed so that different networks may be able to operate in
the same spectrum without significantly degrading the performance
of each other.
[0018] Embodiments contemplate channel access systems and methods
for cognitive relaying in unlicensed bands. One or more embodiments
contemplate managing nodes of a wireless network operating in an
unlicensed band. Embodiments may include sensing an idle channel in
the unlicensed band. Embodiments may also include using the idle
channel for wireless communication.
[0019] Embodiments contemplate a wireless transmit/receive (WTRU)
device that may be configured, at least in part, to establish
communication. The WTRU configuration may comprise sending a signal
to a physical (PHY) layer from at least one higher layer, and
selecting a first access opportunity for a first channel in a first
frequency band in response to the signal. Embodiments also
contemplate that the WTRU configuration may include determining a
state of the first channel, and may also include determining a
second channel in a second frequency band upon a determination that
the state of the first channel is idle. The WTRU configuration may
include sending a signal to a recipient device via the second
channel. Embodiments contemplate that the signal may include
information for reception via the first channel of data
corresponding to the information.
[0020] Embodiments contemplate a wireless transmit/receive device
(WTRU) that may be configured to establish communication. The WTRU
configuration may include sending a signal to a physical (PHY)
layer from at least one higher layer, and selecting a first access
opportunity for a first channel in a first frequency band in
response to the signal. Embodiments contemplate that the
configuration may include determining a state of the first channel,
and determining a second channel in the first frequency band upon a
determination that the state of the first channel is idle.
Embodiments contemplate that the WTRU configuration may include
sending a signal to a recipient device via the second channel. The
signal may include information for reception via the first channel
of data corresponding to the information. Embodiments also
contemplate that the first frequency band may be at least one of an
unlicensed band or a lightly-licensed band.
[0021] Embodiments contemplate a wireless transmit/receive device
(WTRU) that may be configured to establish communication.
Embodiments contemplate that the WTRU configuration may include
detecting a first access opportunity for a first frequency band.
The WTRU configuration may include monitoring for a preamble in the
first access opportunity. The WTRU configuration may include
starting a timer upon the detection of the first access
opportunity. The WTRU configuration may include synchronizing with
a transmitting device upon a detection of the preamble. The WTRU
configuration may include decoding a control channel in the first
frequency band upon the detection of the preamble. Embodiments
contemplate that the first frequency band may be at least one of an
unlicensed band or a lightly-licensed band.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] A more detailed understanding may be had from the following
description, given by way of example in conjunction with the
accompanying drawings wherein:
[0023] FIG. 1A is a system diagram of an example communications
system in which one or more disclosed embodiments may be
implemented;
[0024] FIG. 1B is a system diagram of an example wireless
transmit/receive unit (WTRU) that may be used within the
communications system illustrated in FIG. 1A;
[0025] FIG. 1C is a system diagram of an example radio access
network and an example core network that may be used within the
communications system illustrated in FIG. 1A;
[0026] FIG. 1D is a system diagram of another example radio access
network and an example core network that may be used within the
communications system illustrated in FIG. 1A;
[0027] FIG. 1E is a system diagram of another example radio access
network and an example core network that may be used within the
communications system illustrated in FIG. 1A;
[0028] FIG. 1F shows an illustration of the spectral usage
landscape in Europe which may be used by embodiments;
[0029] FIG. 2 is a band showing unlicensed wireless bands in the
U.S. which may be used by embodiments;
[0030] FIG. 3 is a band spectrum showing time intervals in the
unlicensed band consistent with embodiments;
[0031] FIG. 4 is a band spectrum showing where control data may be
transmitted in the licensed band and maps to a specific subframe in
the unlicensed band consistent with embodiments;
[0032] FIG. 5 is a band spectrum showing exemplary bands consistent
with embodiments;
[0033] FIG. 6 illustrates the events in time that may occur in a
regular WiFi network consistent with embodiments;
[0034] FIG. 7 is a band spectrum showing exemplary bands consistent
with embodiments;
[0035] FIG. 8 is a diagram showing WTRU groups and WiFi nodes
consistent with embodiments;
[0036] FIG. 9 is a diagram showing exemplary transmission from
relay nodes to WTRUs consistent with embodiments;
[0037] FIG. 10 is an exemplary timing diagram consistent with
embodiments;
[0038] FIG. 11 is a diagram showing cellular nodes communicating
with each other, a central controller, and incumbent nodes
consistent with embodiments;
[0039] FIG. 12 are exemplary timing diagrams showing the behavior
of LTE nodes consistent with embodiments;
[0040] FIG. 13 is a graph showing exemplary LTE transmission
duration versus percentage consistent with embodiments;
[0041] FIG. 14 are exemplary timing diagrams consistent with
embodiments;
[0042] FIG. 15 is a graph showing exemplary LTE transmission
duration/LTE attempt interval versus percentage consistent with
embodiments;
[0043] FIG. 16 are exemplary timing diagrams consistent with
embodiments;
[0044] FIG. 17 is a graph showing exemplary LTE transmission
duration versus percentage consistent with embodiments;
[0045] FIG. 18 are exemplary timing diagrams consistent with
embodiments;
[0046] FIG. 19 is a graph showing LTE transmission duration versus
percentage consistent with embodiments;
[0047] FIG. 20A is a graph showing exemplary WiFi throughput (heavy
WiFi network load, load 30 Mbps) consistent with embodiments;
[0048] FIG. 20B is a graph showing exemplary WiFi throughput
(median WiFi network load, load 9 Mbps) consistent with
embodiments;
[0049] FIG. 20C is a graph showing exemplary WiFi throughput (light
WiFi network load, load 4 Mbps) consistent with embodiments;
[0050] FIG. 21 illustrates an exemplary configuration scheme
consistent with embodiments;
[0051] FIG. 21A illustrates an exemplary configuration scheme
consistent with embodiments;
[0052] FIG. 22 illustrates an exemplary configuration scheme
consistent with embodiments; and
[0053] FIG. 23 illustrates an exemplary configuration scheme
consistent with embodiments.
DETAILED DESCRIPTION
[0054] A detailed description of illustrative embodiments will now
be described with reference to the various Figures. Although this
description provides a detailed example of possible
implementations, it should be noted that the details are intended
to be exemplary and in no way limit the scope of the
application.
[0055] FIG. 1A is a diagram of an example communications system 100
in which one or more disclosed embodiments may be implemented. The
communications system 100 may be a multiple access system that
provides content, such as voice, data, video, messaging, broadcast,
etc., to multiple wireless users. The communications system 100 may
enable multiple wireless users to access such content through the
sharing of system resources, including wireless bandwidth. For
example, the communications systems 100 may employ one or more
channel access methods, such as code division multiple access
(CDMA), time division multiple access (TDMA), frequency division
multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrier
FDMA (SC-FDMA), and the like.
[0056] As shown in FIG. 1A, the communications system 100 may
include wireless transmit/receive units (WTRUs) 102a, 102b, 102c,
and/or 102d (which generally or collectively may be referred to as
WTRU 102), a radio access network (RAN) 103/104/105, a core network
106/107/109, a public switched telephone network (PSTN) 108, the
Internet 110, and other networks 112, though it will be appreciated
that the disclosed embodiments contemplate any number of WTRUs,
base stations, networks, and/or network elements. Each of the WTRUs
102a, 102b, 102c, 102d may be any type of device configured to
operate and/or communicate in a wireless environment. By way of
example, the WTRUs 102a, 102b, 102c, 102d may be configured to
transmit and/or receive wireless signals and may include user
equipment (UE), a mobile station, a fixed or mobile subscriber
unit, a pager, a cellular telephone, a personal digital assistant
(PDA), a smartphone, a laptop, a netbook, a personal computer, a
wireless sensor, consumer electronics, and the like.
[0057] The communications systems 100 may also include a base
station 114a and a base station 114b. Each of the base stations
114a, 114b may be any type of device configured to wirelessly
interface with at least one of the WTRUs 102a, 102b, 102c, 102d to
facilitate access to one or more communication networks, such as
the core network 106/107/109, the Internet 110, and/or the networks
112. By way of example, the base stations 114a, 114b may be a base
transceiver station (BTS), a Node-B, an eNode B, a Home Node B, a
Home eNode B, a site controller, an access point (AP), a wireless
router, and the like. While the base stations 114a, 114b are each
depicted as a single element, it will be appreciated that the base
stations 114a, 114b may include any number of interconnected base
stations and/or network elements.
[0058] The base station 114a may be part of the RAN 103/104/105,
which may also include other base stations and/or network elements
(not shown), such as a base station controller (BSC), a radio
network controller (RNC), relay nodes, etc. The base station 114a
and/or the base station 114b may be configured to transmit and/or
receive wireless signals within a particular geographic region,
which may be referred to as a cell (not shown). The cell may
further be divided into cell sectors. For example, the cell
associated with the base station 114a may be divided into three
sectors. Thus, in one embodiment, the base station 114a may include
three transceivers, i.e., one for each sector of the cell. In
another embodiment, the base station 114a may employ multiple-input
multiple output (MIMO) technology and, therefore, may utilize
multiple transceivers for each sector of the cell.
[0059] The base stations 114a, 114b may communicate with one or
more of the WTRUs 102a, 102b, 102c, 102d over an air interface
115/116/117, which may be any suitable wireless communication link
(e.g., radio frequency (RF), microwave, infrared (IR), ultraviolet
(UV), visible light, etc.). The air interface 115/116/117 may be
established using any suitable radio access technology (RAT).
[0060] More specifically, as noted above, the communications system
100 may be a multiple access system and may employ one or more
channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA,
and the like. For example, the base station 114a in the RAN
103/104/105 and the WTRUs 102a, 102b, 102c may implement a radio
technology such as Universal Mobile Telecommunications System
(UMTS) Terrestrial Radio Access (UTRA), which may establish the air
interface 115/116/117 using wideband CDMA (WCDMA). WCDMA may
include communication protocols such as High-Speed Packet Access
(HSPA) and/or Evolved HSPA (HSPA+). HSPA may include High-Speed
Downlink Packet Access (HSDPA) and/or High-Speed Uplink Packet
Access (HSUPA).
[0061] In another embodiment, the base station 114a and the WTRUs
102a, 102b, 102c may implement a radio technology such as Evolved
UMTS Terrestrial Radio Access (E-UTRA), which may establish the air
interface 115/116/117 using Long Term Evolution (LTE) and/or
LTE-Advanced (LTE-A).
[0062] In other embodiments, the base station 114a and the WTRUs
102a, 102b, 102c may implement radio technologies such as IEEE
802.16 (i.e., Worldwide Interoperability for Microwave Access
(WiMAX)), CDMA2000, CDMA2000 1X, CDMA2000 EV-DO, Interim Standard
2000 (IS-2000), Interim Standard 95 (IS-95), Interim Standard 856
(IS-856), Global System for Mobile communications (GSM), Enhanced
Data rates for GSM Evolution (EDGE), GSM EDGE (GERAN), and the
like.
[0063] The base station 114b in FIG. 1A may be a wireless router,
Home Node B, Home eNode B, or access point, for example, and may
utilize any suitable RAT for facilitating wireless connectivity in
a localized area, such as a place of business, a home, a vehicle, a
campus, and the like. In one embodiment, the base station 114b and
the WTRUs 102c, 102d may implement a radio technology such as IEEE
802.11 to establish a wireless local area network (WLAN). In
another embodiment, the base station 114b and the WTRUs 102c, 102d
may implement a radio technology such as IEEE 802.15 to establish a
wireless personal area network (WPAN). In yet another embodiment,
the base station 114b and the WTRUs 102c, 102d may utilize a
cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, etc.)
to establish a picocell or femtocell. As shown in FIG. 1A, the base
station 114b may have a direct connection to the Internet 110.
Thus, the base station 114b may not be required to access the
Internet 110 via the core network 106/107/109.
[0064] The RAN 103/104/105 may be in communication with the core
network 106/107/109, which may be any type of network configured to
provide voice, data, applications, and/or voice over internet
protocol (VoIP) services to one or more of the WTRUs 102a, 102b,
102c, 102d. For example, the core network 106/107/109 may provide
call control, billing services, mobile location-based services,
pre-paid calling, Internet connectivity, video distribution, etc.,
and/or perform high-level security functions, such as user
authentication. Although not shown in FIG. 1A, it will be
appreciated that the RAN 103/104/105 and/or the core network
106/107/109 may be in direct or indirect communication with other
RANs that employ the same RAT as the RAN 103/104/105 or a different
RAT. For example, in addition to being connected to the RAN
103/104/105, which may be utilizing an E-UTRA radio technology, the
core network 106/107/109 may also be in communication with another
RAN (not shown) employing a GSM radio technology.
[0065] The core network 106/107/109 may also serve as a gateway for
the WTRUs 102a, 102b, 102c, 102d to access the PSTN 108, the
Internet 110, and/or other networks 112. The PSTN 108 may include
circuit-switched telephone networks that provide plain old
telephone service (POTS). The Internet 110 may include a global
system of interconnected computer networks and devices that use
common communication protocols, such as the transmission control
protocol (TCP), user datagram protocol (UDP) and the internet
protocol (IP) in the TCP/IP internet protocol suite. The networks
112 may include wired or wireless communications networks owned
and/or operated by other service providers. For example, the
networks 112 may include another core network connected to one or
more RANs, which may employ the same RAT as the RAN 103/104/105 or
a different RAT.
[0066] Some or all of the WTRUs 102a, 102b, 102c, 102d in the
communications system 100 may include multi-mode capabilities,
i.e., the WTRUs 102a, 102b, 102c, 102d may include multiple
transceivers for communicating with different wireless networks
over different wireless links. For example, the WTRU 102c shown in
FIG. 1A may be configured to communicate with the base station
114a, which may employ a cellular-based radio technology, and with
the base station 114b, which may employ an IEEE 802 radio
technology.
[0067] FIG. 1B is a system diagram of an example WTRU 102. As shown
in FIG. 1B, the WTRU 102 may include a processor 118, a transceiver
120, a transmit/receive element 122, a speaker/microphone 124, a
keypad 126, a display/touchpad 128, non-removable memory 130,
removable memory 132, a power source 134, a global positioning
system (GPS) chipset 136, and other peripherals 138. It will be
appreciated that the WTRU 102 may include any sub-combination of
the foregoing elements while remaining consistent with an
embodiment. Also, embodiments contemplate that the base stations
114a and 114b, and/or the nodes that base stations 114a and 114b
may represent, such as but not limited to transceiver station
(BTS), a Node-B, a site controller, an access point (AP), a home
node-B, an evolved home node-B (eNodeB), a home evolved node-B
(HeNB), a home evolved node-B gateway, and proxy nodes, among
others, may include some or all of the elements depicted in FIG. 1B
and described herein.
[0068] The processor 118 may be a general purpose processor, a
special purpose processor, a conventional processor, a digital
signal processor (DSP), a plurality of microprocessors, one or more
microprocessors in association with a DSP core, a controller, a
microcontroller, Application Specific Integrated Circuits (ASICs),
Field Programmable Gate Array (FPGAs) circuits, any other type of
integrated circuit (IC), a state machine, and the like. The
processor 118 may perform signal coding, data processing, power
control, input/output processing, and/or any other functionality
that enables the WTRU 102 to operate in a wireless environment. The
processor 118 may be coupled to the transceiver 120, which may be
coupled to the transmit/receive element 122. While FIG. 1B depicts
the processor 118 and the transceiver 120 as separate components,
it will be appreciated that the processor 118 and the transceiver
120 may be integrated together in an electronic package or
chip.
[0069] The transmit/receive element 122 may be configured to
transmit signals to, or receive signals from, a base station (e.g.,
the base station 114a) over the air interface 115/116/117. For
example, in one embodiment, the transmit/receive element 122 may be
an antenna configured to transmit and/or receive RF signals. In
another embodiment, the transmit/receive element 122 may be an
emitter/detector configured to transmit and/or receive IR, UV, or
visible light signals, for example. In yet another embodiment, the
transmit/receive element 122 may be configured to transmit and
receive both RF and light signals. It will be appreciated that the
transmit/receive element 122 may be configured to transmit and/or
receive any combination of wireless signals.
[0070] In addition, although the transmit/receive element 122 is
depicted in FIG. 1B as a single element, the WTRU 102 may include
any number of transmit/receive elements 122. More specifically, the
WTRU 102 may employ MIMO technology. Thus, in one embodiment, the
WTRU 102 may include two or more transmit/receive elements 122
(e.g., multiple antennas) for transmitting and receiving wireless
signals over the air interface 115/116/117.
[0071] The transceiver 120 may be configured to modulate the
signals that are to be transmitted by the transmit/receive element
122 and to demodulate the signals that are received by the
transmit/receive element 122. As noted above, the WTRU 102 may have
multi-mode capabilities. Thus, the transceiver 120 may include
multiple transceivers for enabling the WTRU 102 to communicate via
multiple RATs, such as UTRA and IEEE 802.11, for example.
[0072] The processor 118 of the WTRU 102 may be coupled to, and may
receive user input data from, the speaker/microphone 124, the
keypad 126, and/or the display/touchpad 128 (e.g., a liquid crystal
display (LCD) display unit or organic light-emitting diode (OLED)
display unit). The processor 118 may also output user data to the
speaker/microphone 124, the keypad 126, and/or the display/touchpad
128. In addition, the processor 118 may access information from,
and store data in, any type of suitable memory, such as the
non-removable memory 130 and/or the removable memory 132. The
non-removable memory 130 may include random-access memory (RAM),
read-only memory (ROM), a hard disk, or any other type of memory
storage device. The removable memory 132 may include a subscriber
identity module (SIM) card, a memory stick, a secure digital (SD)
memory card, and the like. In other embodiments, the processor 118
may access information from, and store data in, memory that is not
physically located on the WTRU 102, such as on a server or a home
computer (not shown).
[0073] The processor 118 may receive power from the power source
134, and may be configured to distribute and/or control the power
to the other components in the WTRU 102. The power source 134 may
be any suitable device for powering the WTRU 102. For example, the
power source 134 may include one or more dry cell batteries (e.g.,
nickel-cadmium (NiCd), nickel-zinc (NiZn), nickel metal hydride
(NiMH), lithium-ion (Li-ion), etc.), solar cells, fuel cells, and
the like.
[0074] The processor 118 may also be coupled to the GPS chipset
136, which may be configured to provide location information (e.g.,
longitude and latitude) regarding the current location of the WTRU
102. In addition to, or in lieu of, the information from the GPS
chipset 136, the WTRU 102 may receive location information over the
air interface 115/116/117 from a base station (e.g., base stations
114a, 114b) and/or determine its location based on the timing of
the signals being received from two or more nearby base stations.
It will be appreciated that the WTRU 102 may acquire location
information by way of any suitable location-determination method
while remaining consistent with an embodiment.
[0075] The processor 118 may further be coupled to other
peripherals 138, which may include one or more software and/or
hardware modules that provide additional features, functionality
and/or wired or wireless connectivity. For example, the peripherals
138 may include an accelerometer, an e-compass, a satellite
transceiver, a digital camera (for photographs or video), a
universal serial bus (USB) port, a vibration device, a television
transceiver, a hands free headset, a Bluetooth.RTM. module, a
frequency modulated (FM) radio unit, a digital music player, a
media player, a video game player module, an Internet browser, and
the like.
[0076] FIG. 1C is a system diagram of the RAN 103 and the core
network 106 according to an embodiment. As noted above, the RAN 103
may employ a UTRA radio technology to communicate with the WTRUs
102a, 102b, 102c over the air interface 115. The RAN 103 may also
be in communication with the core network 106. As shown in FIG. 1C,
the RAN 103 may include Node-Bs 140a, 140b, 140c, which may each
include one or more transceivers for communicating with the WTRUs
102a, 102b, 102c over the air interface 115. The Node-Bs 140a,
140b, 140c may each be associated with a particular cell (not
shown) within the RAN 103. The RAN 103 may also include RNCs 142a,
142b. It will be appreciated that the RAN 103 may include any
number of Node-Bs and RNCs while remaining consistent with an
embodiment.
[0077] As shown in FIG. 1C, the Node-Bs 140a, 140b may be in
communication with the RNC 142a. Additionally, the Node-B 140c may
be in communication with the RNC 142b. The Node-Bs 140a, 140b, 140c
may communicate with the respective RNCs 142a, 142b via an Iub
interface. The RNCs 142a, 142b may be in communication with one
another via an Iur interface. Each of the RNCs 142a, 142b may be
configured to control the respective Node-Bs 140a, 140b, 140c to
which it is connected. In addition, each of the RNCs 142a, 142b may
be configured to carry out or support other functionality, such as
outer loop power control, load control, admission control, packet
scheduling, handover control, macrodiversity, security functions,
data encryption, and the like.
[0078] The core network 106 shown in FIG. 1C may include a media
gateway (MGW) 144, a mobile switching center (MSC) 146, a serving
GPRS support node (SGSN) 148, and/or a gateway GPRS support node
(GGSN) 150. While each of the foregoing elements are depicted as
part of the core network 106, it will be appreciated that any one
of these elements may be owned and/or operated by an entity other
than the core network operator.
[0079] The RNC 142a in the RAN 103 may be connected to the MSC 146
in the core network 106 via an IuCS interface. The MSC 146 may be
connected to the MGW 144. The MSC 146 and the MGW 144 may provide
the WTRUs 102a, 102b, 102c with access to circuit-switched
networks, such as the PSTN 108, to facilitate communications
between the WTRUs 102a, 102b, 102c and traditional land-line
communications devices.
[0080] The RNC 142a in the RAN 103 may also be connected to the
SGSN 148 in the core network 106 via an IuPS interface. The SGSN
148 may be connected to the GGSN 150. The SGSN 148 and the GGSN 150
may provide the WTRUs 102a, 102b, 102c with access to
packet-switched networks, such as the Internet 110, to facilitate
communications between and the WTRUs 102a, 102b, 102c and
IP-enabled devices.
[0081] As noted above, the core network 106 may also be connected
to the networks 112, which may include other wired or wireless
networks that are owned and/or operated by other service
providers.
[0082] FIG. 1D is a system diagram of the RAN 104 and the core
network 107 according to an embodiment. As noted above, the RAN 104
may employ an E-UTRA radio technology to communicate with the WTRUs
102a, 102b, and 102c over the air interface 116. The RAN 104 may
also be in communication with the core network 107.
[0083] The RAN 104 may include eNode-Bs 160a, 160b, 160c, though it
will be appreciated that the RAN 104 may include any number of
eNode-Bs while remaining consistent with an embodiment. The
eNode-Bs 160a, 160b, 160c may each include one or more transceivers
for communicating with the WTRUs 102a, 102b, 102c over the air
interface 116. In one embodiment, the eNode-Bs 160a, 160b, 160c may
implement MIMO technology. Thus, the eNode-B 160a, for example, may
use multiple antennas to transmit wireless signals to, and receive
wireless signals from, the WTRU 102a.
[0084] Each of the eNode-Bs 160a, 160b, and 160c may be associated
with a particular cell (not shown) and may be configured to handle
radio resource management decisions, handover decisions, scheduling
of users in the uplink and/or downlink, and the like. As shown in
FIG. 1D, the eNode-Bs 160a, 160b, 160c may communicate with one
another over an X2 interface.
[0085] The core network 107 shown in FIG. 1D may include a mobility
management gateway (MME) 162, a serving gateway 164, and a packet
data network (PDN) gateway 166. While each of the foregoing
elements are depicted as part of the core network 107, it will be
appreciated that any one of these elements may be owned and/or
operated by an entity other than the core network operator.
[0086] The MME 162 may be connected to each of the eNode-Bs 160a,
160b, and 160c in the RAN 104 via an S1 interface and may serve as
a control node. For example, the MME 162 may be responsible for
authenticating users of the WTRUs 102a, 102b, 102c, bearer
activation/deactivation, selecting a particular serving gateway
during an initial attach of the WTRUs 102a, 102b, 102c, and the
like. The MME 162 may also provide a control plane function for
switching between the RAN 104 and other RANs (not shown) that
employ other radio technologies, such as GSM or WCDMA.
[0087] The serving gateway 164 may be connected to each of the
eNode-Bs 160a, 160b, and 160c in the RAN 104 via the S1 interface.
The serving gateway 164 may generally route and forward user data
packets to/from the WTRUs 102a, 102b, 102c. The serving gateway 164
may also perform other functions, such as anchoring user planes
during inter-eNode B handovers, triggering paging when downlink
data is available for the WTRUs 102a, 102b, 102c, managing and
storing contexts of the WTRUs 102a, 102b, 102c, and the like.
[0088] The serving gateway 164 may also be connected to the PDN
gateway 166, which may provide the WTRUs 102a, 102b, 102c with
access to packet-switched networks, such as the Internet 110, to
facilitate communications between the WTRUs 102a, 102b, 102c and
IP-enabled devices.
[0089] The core network 107 may facilitate communications with
other networks. For example, the core network 107 may provide the
WTRUs 102a, 102b, 102c with access to circuit-switched networks,
such as the PSTN 108, to facilitate communications between the
WTRUs 102a, 102b, 102c and traditional land-line communications
devices. For example, the core network 107 may include, or may
communicate with, an IP gateway (e.g., an IP multimedia subsystem
(IMS) server) that serves as an interface between the core network
107 and the PSTN 108. In addition, the core network 107 may provide
the WTRUs 102a, 102b, 102c with access to the networks 112, which
may include other wired or wireless networks that are owned and/or
operated by other service providers.
[0090] FIG. 1E is a system diagram of the RAN 105 and the core
network 109 according to an embodiment. The RAN 105 may be an
access service network (ASN) that employs IEEE 802.16 radio
technology to communicate with the WTRUs 102a, 102b, and 102c over
the air interface 117. As will be further discussed below, the
communication links between the different functional entities of
the WTRUs 102a, 102b, 102c, the RAN 105, and the core network 109
may be defined as reference points.
[0091] As shown in FIG. 1E, the RAN 105 may include base stations
180a, 180b, 180c, and an ASN gateway 182, though it will be
appreciated that the RAN 105 may include any number of base
stations and ASN gateways while remaining consistent with an
embodiment. The base stations 180a, 180b, 180c may each be
associated with a particular cell (not shown) in the RAN 105 and
may each include one or more transceivers for communicating with
the WTRUs 102a, 102b, 102c over the air interface 117. In one
embodiment, the base stations 180a, 180b, 180c may implement MIMO
technology. Thus, the base station 180a, for example, may use
multiple antennas to transmit wireless signals to, and receive
wireless signals from, the WTRU 102a. The base stations 180a, 180b,
180c may also provide mobility management functions, such as
handoff triggering, tunnel establishment, radio resource
management, traffic classification, quality of service (QoS) policy
enforcement, and the like. The ASN gateway 182 may serve as a
traffic aggregation point and may be responsible for paging,
caching of subscriber profiles, routing to the core network 109,
and the like.
[0092] The air interface 117 between the WTRUs 102a, 102b, 102c and
the RAN 105 may be defined as an R1 reference point that implements
the IEEE 802.16 specification. In addition, each of the WTRUs 102a,
102b, and 102c may establish a logical interface (not shown) with
the core network 109. The logical interface between the WTRUs 102a,
102b, 102c and the core network 109 may be defined as an R2
reference point, which may be used for authentication,
authorization, IP host configuration management, and/or mobility
management.
[0093] The communication link between each of the base stations
180a, 180b, and 180c may be defined as an R8 reference point that
includes protocols for facilitating WTRU handovers and the transfer
of data between base stations. The communication link between the
base stations 180a, 180b, 180c and the ASN gateway 182 may be
defined as an R6 reference point. The R6 reference point may
include protocols for facilitating mobility management based on
mobility events associated with each of the WTRUs 102a, 102b,
102c.
[0094] As shown in FIG. 1E, the RAN 105 may be connected to the
core network 109. The communication link between the RAN 105 and
the core network 109 may defined as an R3 reference point that
includes protocols for facilitating data transfer and mobility
management capabilities, for example. The core network 109 may
include a mobile IP home agent (MIP-HA) 184, an authentication,
authorization, accounting (AAA) server 186, and a gateway 188.
While each of the foregoing elements are depicted as part of the
core network 109, it will be appreciated that any one of these
elements may be owned and/or operated by an entity other than the
core network operator.
[0095] The MIP-HA may be responsible for IP address management, and
may enable the WTRUs 102a, 102b, and 102c to roam between different
ASNs and/or different core networks. The MIP-HA 184 may provide the
WTRUs 102a, 102b, 102c with access to packet-switched networks,
such as the Internet 110, to facilitate communications between the
WTRUs 102a, 102b, 102c and IP-enabled devices. The AAA server 186
may be responsible for user authentication and for supporting user
services. The gateway 188 may facilitate interworking with other
networks. For example, the gateway 188 may provide the WTRUs 102a,
102b, 102c with access to circuit-switched networks, such as the
PSTN 108, to facilitate communications between the WTRUs 102a,
102b, 102c and traditional land-line communications devices. In
addition, the gateway 188 may provide the WTRUs 102a, 102b, 102c
with access to the networks 112, which may include other wired or
wireless networks that are owned and/or operated by other service
providers.
[0096] Although not shown in FIG. 1E, it will be appreciated that
the RAN 105 may be connected to other ASNs and the core network 109
may be connected to other core networks. The communication link
between the RAN 105 the other ASNs may be defined as an R4
reference point, which may include protocols for coordinating the
mobility of the WTRUs 102a, 102b, 102c between the RAN 105 and the
other ASNs. The communication link between the core network 109 and
the other core networks may be defined as an R5 reference, which
may include protocols for facilitating interworking between home
core networks and visited core networks.
[0097] Embodiments contemplate that, perhaps because of the
increasing number of users and data-rich applications, licensed
spectrum availability may be limited in near future, and it would
be beneficial to enable users to seamlessly and opportunistically
roam across various wireless access networks in the search for more
throughput and/or cheaper bandwidth. Embodiments recognize that
close to half of the allocated spectrum space is unutilized and/or
under-utilized. By way of example, and not limitation, FIG. 1F
shows an exemplary illustration of the vast spectral usage
landscape in Europe.
[0098] Embodiments contemplate that secondary utilization of unused
spectrum may require efficient detection and sharing without
harmful interference with other users. For these and other reasons,
embodiments contemplate a cognitive radio which may be defined as a
communication system that collects information such as channel
conditions, spectrum availability, activity, codebooks, messages of
other nodes with which it shares the spectrum, etc., from its
environment.
[0099] Embodiments contemplate systems and methods for adapting
transmission according to a dynamic radio environment to improve
utilization of limited radio resources.
[0100] Embodiments contemplate methods and systems by which
cognitive radios may improve system performance by intelligently
utilizing information such as, but not limited to, channel
conditions, spectrum availability, activity, codebooks, messages of
other nodes with which it shares the spectrum, etc. from the
environment. Contemplated cognitive radio transceivers may be able
to adapt its transmission according to the dynamic radio
environment to maximize the utilization of the limited radio
resources while providing flexibility in wireless access, for
example.
[0101] FIG. 2 illustrates a graph of unlicensed bands in the United
States (US) and the legacy or other protocols that may operate in
the various illustrated bands. These bands are broadly regulated
under the industrial, scientific, and medical (ISM) and the
Unlicensed National Information Infrastructure (U-NII) regulations,
both defined by the FCC.
[0102] Embodiments contemplate that cognitive behavior may be
grouped into three categories, for example, and each of which may
exploit varying degrees of knowledge of the wireless environment at
the cognitive users: [0103] Overlay cognitive radio: Cognitive and
primary nodes may transmit concurrently by means of some kind of
cooperation. Cognitive nodes, for example, may help the primary
nodes complete the primary transmissions faster and then utilize
the vacant resources to send their own messages. [0104] Underlay
cognitive radio: Cognitive nodes may operate simultaneously with
the primary nodes with the potential condition that the
transmission of the primary users is not disrupted by the cognitive
nodes. For example, cognitive nodes may transmit in the primary
spectrum but with very low power. [0105] Interweave cognitive
radio: Cognitive nodes may find and use spectral holes not used by
the primary transmitters.
[0106] Embodiments also recognize there may be different possible
parts of spectrum to choose from for transmission by cognitive
radio node. In one or more embodiments, it may be assumed that
unlicensed bands are available for the radio node (unlicensed band
cognitive radio), and perhaps in some embodiments only unlicensed
bands are available. Also, in one or more embodiments, licensed
bands may also available (e.g., lightly licensed and/or unlicensed
bands). Embodiments contemplate that cognitive radio may allow
usage of unused unlicensed bands by cellular LTE relay node devices
and terminals.
[0107] Embodiments contemplate systems and methods that address
relaying protocols and system design considerations that may enable
cognitive use of unlicensed/lightly licensed spectrum by cellular
nodes. Specifically, embodiments contemplate extensions for one or
more cellular protocols that may allow sensing based access of the
unlicensed or lightly licensed spectrum. Embodiments also
contemplate that general solutions/techniques that may enable
spectrum sharing among networks may be applicable to other
scenarios as well (for example dynamic sharing of the cellular
spectrum). Unlicensed spectrum may be used by other communications
devices. Specifically, the 2.4 GHz and the 5 GHz ISM bands may be
used by 802.11 local area networks besides some other networks, for
example. Embodiments recognize that the cellular network may not
know if and/or how the unlicensed band may be used via any
communication techniques between them, if any.
[0108] Embodiments contemplate that when cellular devices also
start using these bands, the system may be implemented such that
the effect of the cellular communications on the incumbent networks
can be minimal. As an example, cellular nodes may not create
excessive interference on the incumbent nodes or disturb ongoing
transmissions significantly. Embodiments recognize that local area
networks usually use a "listen before talk" protocol for channel
access to minimize collisions. Cellular nodes may be able to use
similar techniques so that the unlicensed channel may be used when
it is free. Embodiments contemplate approaches that may be
different from the cellular architecture where the medium access is
controlled by a central transmitter. Embodiments contemplate one or
more sensing and accessing mechanisms.
[0109] Embodiments contemplate that the use of the one or more new
bands would have been useful for cellular communications. For
example, embodiments contemplate the reduction of the interference
in the cellular system. More specifically, embodiments contemplate
that cognitive relaying may be used to reduce the interference on
one or more cell-edge WTRUs by utilizing the newly available
spectrum to transmit part (or all) of the primary node's (e.g.,
base station's) message. The cognitive relay may achieve this by
transmitting with reduced (or perhaps zero) power, or use less
frequency resources (e.g., carrier frequencies/PRBs) in the
cellular band and compensate for the loss by transmitting in the
new spectrum.
[0110] Embodiments contemplate that the WTRU that may receive
transmission from the cognitive relay may experience less
interference in the new spectrum. As an example, if the band is the
ISM band and a medium access scheme based on interference avoidance
and carrier sensing as described herein is used, this may result in
more favorable interference-free conditions than the cellular
spectrum. Embodiments also contemplate that with this kind of
transmission, the interference in the cellular band due to the
relay transmission may be reduced resulting in an improvement in
the capacity of other primary cell-edge nodes. In fact, the reduced
interference may benefit one or more WTRUs, and in some embodiments
perhaps all the WTRUs, of the whole network, but the closest nodes
may experience the largest benefits.
[0111] Embodiments also contemplate capacity improvement. Cognitive
relays may use the extra available spectrum to transmit additional
data to increase the capacity of the cell-edge WTRUs. For example,
the cognitive relay may transmit additional bits to the WTRU
through the new spectrum and improve the capacity of the WTRU.
Depending on the relaying technique, capacity may be enhanced
without increasing the total transmit power.
[0112] One or more embodiments may enable the access and use of the
unlicensed spectrum for transmission and reception by cellular
devices. Embodiments recognize that channel access mechanisms may
differ in the downlink and uplink directions. In the downlink, the
cellular user may have to contend with other cellular and
non-cellular users of the spectrum. In the uplink direction,
several WTRUs trying to communicate with a common receiver may
attempt to access the channel simultaneously resulting in
collisions. Therefore, embodiments contemplate avoiding or
minimizing the resulting collisions. In the present disclosure,
downlink is defined as the direction from the relay to the WTRUs
and uplink is defined as the direction from the WTRUs to the relay.
The relay may be an infrastructure relay or simply a WTRU operating
as a relay. When the relay is also a WTRU, it is called a helper
WTRU and the downlink and uplink definitions apply similarly. The
downlink and uplink transmissions (or transmit/receive) may be
multiplexed in time as in Time Domain Duplexing (TDD) systems or in
frequency as in Frequency Domain Duplexing (FDD) systems.
[0113] Embodiments contemplate channel access mechanisms for the
cellular nodes operating in an unlicensed band. One or more of the
contemplate channel access mechanisms may generally include at
least two parts; contention with the nodes operating in the same
spectrum that may use different protocols or with the nodes that
use the same protocol but may not be able to communicate with each
other; and contention among the WTRUs to access the spectrum. The
first part may include carrier sensing and other methods to
identify an idle channel. The second part may include methods that
enable simultaneous usage of the idle channel (perhaps as in the
uplink direction where several WTRUs may need to communicate with a
single receiver). The downlink and uplink communications among the
cellular nodes in the unlicensed spectrum may be separated in the
frequency or time domains. FDD or TDD may be used for this
purpose.
[0114] Embodiments contemplate access opportunities may be fixed
(e.g. in time) or semi-statically configured. An example is shown
in FIG. 3 where the time intervals denoted as indicated in the
unlicensed band may be access opportunities. These intervals may be
candidate points in time when the transmitter may start sensing the
channel and initiate a transmission in the unlicensed band if the
channel is found to be idle, for example. The time interval may be
large enough to compensate for sensing, MAC processing, propagation
delays, and/or RX/TX turnaround time, for example. To be able to
sense one or more, or all, WiFi transmissions, the total sensing
interval may be larger than the Short Interframe Space (SIFS)
duration. If the sensing interval may not be continuous, then the
difference between first and last points in time when sensing is
performed may be larger than the SIFS duration.
[0115] In one or more embodiments, it may be assumed that the
subframe timing in the unlicensed band is known. This may be
achieved by deducing the timing in the unlicensed band from the
timing of the licensed band. In this case, the beginning of a
subframe and/or OFDM symbol in the unlicensed band may have a fixed
offset to the beginning of a subframe and/or OFDM symbol in the
licensed band. One or more, and perhaps all, of the cellular nodes
operating in the unlicensed band may be synchronized. This is
achieved because these nodes may attain time and frequency
synchronization from the licensed band.
[0116] Points in time may be defined that may be specific access
opportunities. An "access opportunity" is defined as a time
interval when the node intending to initiate a transmission may
sense the channel to see if it is available, and starts
transmission if the channel is found to be idle.
[0117] In one or more embodiments, access opportunities may be
fixed or semi-statically configured. An example is shown in FIG. 3
where the indicated time intervals in the unlicensed band may be
access opportunities. These intervals may be candidate points in
time when the transmitter may start sensing the channel and
initiate a transmission in the unlicensed band if the channel is
found to be idle. The time interval may be large enough to
compensate for sensing, MAC processing, propagation delays and
RX/TX turnaround time. To be able to sense one or more WiFi
transmission, or perhaps all WiFi transmissions, the total sensing
interval may be larger than the SIFS duration. If the sensing
interval may not be continuous, then the difference between first
and last points in time when sensing is performed may be larger
than the SIFS duration, for example.
[0118] In addition to the channel access mechanism, the
corresponding frame structure and control signaling to support
transmission in the unlicensed band also may be specified. One or
more embodiments contemplate that the control signaling may be
transmitted in the licensed band, and in some embodiments perhaps
only in the licensed band (similar to control signaling when
component carrier aggregation may be used in LTE-Advanced). The
transmission that takes place in the unlicensed band may be
controlled by the signaling in the licensed band. To achieve this,
the subframe timings of the licensed and unlicensed bands may have
a fixed offset. This is illustrated in FIG. 4 where the control
data may be transmitted in the licensed band and may map to a
specific subframe in the unlicensed band.
[0119] When this approach is used, embodiments contemplate that
there may be a gap between the time when the channel is sensed and
found to be idle and the time when the control data is transmitted
in the licensed band. The transmitter may occupy the channel in the
unlicensed band during this gap to ensure that the channel may be
available when the control data is transmitted. One or more
embodiments contemplate transmitting some data, such as padding
bits, during this gap. One or more embodiments may assume that the
receivers are not aware of any transmission until they decode the
control channel. After the receivers decode the control channel,
they can get the corresponding transmission in the unlicensed band.
From this point on, transmission may continue in a regular manner
as illustrated in FIG. 4.
[0120] Embodiments contemplate one or more procedures for a
transmitting node may include the PHY layer of the transmitter
receiving a request from the MAC and/or higher layers to sense the
unlicensed band for a possible transmission. An access opportunity
may be chosen and sensing may be performed. Embodiments also
contemplate that if the channel is found to be busy, the
transmitter may waits for the next access opportunity to sense the
channel. Embodiments contemplate that the determination that a
transmitter is in a "busy" state may include determining that the
transmitter may be transmitting, among other activities.
Embodiments recognize that when a channel is in a busy state, at
least one transmitter may be emitting energy in that channel in the
area of interest, for example. Further, embodiments contemplate
that if the channel is found to be idle, the transmitter may start
transmitting padding bits in the idle channel to keep the channel
busy. The padding bits may include random data or a known preamble
(like an 802.11 preamble, for example) to allow other users (e.g.,
802.11) of the spectrum to adjust their Network Allocation Vector
(NAV). Embodiments also contemplate that in the next available
control channel in the licensed band, the transmitter may send the
necessary allocation information to the scheduled WTRUs for
reception in the unlicensed band. The corresponding data in the
scheduled resources may be transmitted in the unlicensed band.
[0121] Embodiments contemplate one or more procedures for receiving
nodes may include the receiving node receiving and decoding the
control channel in the licensed band. Further, embodiments
contemplate that if resources are scheduled in the unlicensed band,
the receiving nodes may start receiving in the unlicensed band and
perform the required receive operations. The corresponding
feedback, such as ACK/NACK or channel state/quality information may
be transmitted in the licensed band. Also, embodiments contemplate
that if a preamble that may be decoded by 802.11 nodes is
transmitted, for example, then the preamble may be used to reserve
the channel for a specific amount of time by setting the packet
length data field in the preamble. In this case, two way
communications may proceed until the end of the specified time.
[0122] Embodiments contemplate that as the amount of traffic in the
channel becomes higher, latency in accessing the channel may
increase due to the low probability of finding the channel
available at a given access opportunity. This may require that
higher layers forward delay-tolerant data on this channel so that
quality of service may not be degraded.
[0123] Embodiments contemplate one or more methods in which control
signaling may be transmitted in the unlicensed band. Embodiments
contemplate that the transmitter may start sensing the channel at a
specified access opportunity. If the channel is found to be idle,
then the transmitter may start transmitting a preamble in the
unlicensed band as shown in FIG. 5. The preamble may be a sequence
known by the transmitter and some or all of the receivers and may
be used to inform the receivers of an incoming transmission. The
preamble may also be used for synchronization.
[0124] Embodiments contemplate that the transmitter may not inform
the receivers in the control channel of the licensed band; so the
receiving nodes may be continuously receiving in the unlicensed
band and processing the incoming signal to decode the preamble
sequence. The access opportunities may be known by some or all the
nodes and a preamble search may be performed by some or all of the
receive nodes around these intervals. If the preamble cannot be
found, receiving may be terminated and postponed until the next
opportunity, for example.
[0125] Embodiments contemplate that the preamble may be similar to
the synchronization sequence used in LTE and may be transmitted in
a portion of the total bandwidth of the channel, for example. In
addition to indicating the beginning of a transmission, the
sequence may also be used for frequency synchronization. After the
receivers decode the preamble, the data transmission may start. One
or more control channels may be transmitted in the unlicensed band
followed by data transmission.
[0126] Embodiments contemplate one or more procedures for
transmitting node that may include the PHY layer of the transmitter
receiving a request from the MAC and/or higher layers to sense the
unlicensed band for a possible transmission. An access opportunity
may be chosen and sensing may be performed. Embodiments contemplate
that if the channel is found to be busy, the transmitter may wait
for the next access opportunity. Also, embodiments contemplate that
if the channel is found to be idle, the transmitter may start
transmitting a preamble in the idle channel. The preamble may
include specific sequence(s) that may be known by the receiving
nodes. Embodiments contemplate that data transmission may start in
the unlicensed band. In one or more embodiments, control signaling
may be transmitted in the unlicensed band prior to the data.
Alternatively or additionally, in one or more embodiments, control
signaling may be transmitted in the licensed band as described in
previous embodiments.
[0127] Embodiments contemplate one or more procedures for receiving
nodes that may include--during an access opportunity--the receiving
nodes may start receiving in the unlicensed band and may search for
the preamble. A timer may also be started to measure the time spent
for searching the preamble. Embodiments also contemplate that if
the preamble is not detected and/or the timer expires, preamble
searching may be terminated and/or postponed until the next
opportunity. Embodiments also contemplate that if the preamble is
detected, then synchronization may be achieved. Embodiments also
contemplate that control channel may be decoded to find out the
properties of the incoming transmission in the unlicensed band,
among other reasons. The control channel may be transmitted in the
unlicensed band prior to the data transmission or in the licensed
band. Embodiments contemplate that the corresponding feedback, such
as ACK/NACK or channel state/quality information, for example, may
be transmitted in the licensed band.
[0128] In the one or more embodiments, the transmitter may sense
the channel at fixed and/or predefined intervals. Embodiments also
contemplate that the channel may be idle or busy at these
intervals. Embodiments recognize that if the traffic in the channel
is not high, then the probability of finding the channel idle at
these intervals may be large. However, at highly loaded channels,
the channel may be used most of the time. By way of example, and
not limitation, such embodiments may be referred to as
variable-time sensing (or continuous sensing) techniques.
[0129] FIG. 6 illustrates the events in time that may occur in a
regular WiFi network, for example. In a highly loaded system as
illustrated in part "a" of FIG. 6, after a data packet is
transmitted from one of the stations, an ACK packet may be fed back
after SIFS amount of time. Then, the remaining stations contend for
the next transmission which may occur after a DIFS amount of time.
Embodiments contemplate that the data packets could last up to
several milliseconds (ms). Embodiments also contemplate that an
opportunity for the cellular nodes to access (or "grab") the
channel, and in some embodiments perhaps the only opportunity for
the cellular nodes to grab the channel, may be when the WiFi
stations are contending for the next transmission. One or more
embodiments contemplate that it may not be desirable to grab the
channel before an ACK packet is fed back because this may cause the
data packet to be lost. In such scenarios, fixed-time sensing may
have a lower probability of finding the channel idle. However, in a
lightly or moderately loaded WiFi network, the channel may stay
idle between consecutive transmissions as illustrated in part b of
FIG. 6--and thus embodiments contemplate that fixed-time sensing
may find the channel idle with a higher probability.
[0130] Embodiments contemplate one or more different channel access
mechanisms in which the duration of sensing may not be fixed. In
one or more embodiments, a transmitter may start sensing the
channel at a specific time instance (which may be called an "access
opportunity" as described previously) and may continue performing
the sensing operation until the channel becomes idle, for example.
Embodiments contemplate that a maximum sensing duration limit may
be defined so that the transmitter may terminate sensing if the
channel does not become available in this duration.
[0131] Embodiments contemplate that the time instances when sensing
may start may be specified semi-statically and/or signaled in the
control channel as in the fixed-time sensing, for example. This
scheme is illustrated in FIG. 7. In FIG. 7, the transmitter may
start sensing the channel at time T.sub.o and may find the channel
idle after .DELTA.T seconds. If the channel does not become
available after .DELTA.T.sub.max seconds (not shown), then the
transmitter may cease sensing and may resume sensing at the next
access opportunity, for example. In one or more embodiments, the
frame structure and control channel may be similar to the
fixed-time sensing embodiments.
[0132] Embodiments contemplate that one or more control channels
may be transmitted in the licensed band as described previously.
Embodiments further contemplate that the PHY layer of the
transmitter may receive a request from the MAC and/or higher layers
to sense the unlicensed band for a possible transmission. An access
opportunity may be chosen and sensing may be performed. A timer may
be started where the value of the timer may be set to the
configured maximum sensing duration and the transmitter may start
sensing the channel. Embodiments also contemplate that if the timer
expires and a channel may be busy, the transmitter may wait for the
next access opportunity. Embodiments also contemplate that if the
channel is found to be idle before the timer expires, the
transmitter may start transmitting padding bits in the idle channel
to keep the channel busy. The padding bits may include random data.
Embodiments further contemplate that in a subsequently available
control channel in the licensed band, and in one or more
embodiments perhaps the next available control channel in the
licensed band, the transmitter may send the necessary allocation
information to the scheduled WTRUs for reception in the unlicensed
band. The corresponding data in the scheduled resources may be
transmitted in the unlicensed band, for example.
[0133] Embodiments further contemplate one or more embodiments for
one or more receiving nodes in which one or more receiving nodes
may receive and may decode the control channel in the licensed
band. Embodiments further contemplate that if resources are
scheduled in the unlicensed band, the receiving nodes may start
receiving in the unlicensed band and may perform the required
receive operations. The corresponding feedback, such as ACK/NACK or
channel state/quality information, may be transmitted in the
licensed band.
[0134] Embodiments further contemplate that one or more control
channels may be transmitted in the unlicensed band as described
previously. In one or more embodiments the PHY layer of a
transmitter may receive a request from the MAC and/or higher layers
to sense the unlicensed band for a possible transmission. An access
opportunity may be chosen and sensing may be performed. A timer may
be started where the value of the timer may be set to a configured
maximum sensing duration. And embodiments contemplate that the
transmitter may start sensing the channel. Embodiments also
contemplate that if the timer expires and the channel is busy, the
transmitter may wait for the next access opportunity. Embodiments
also contemplate that if the channel is found to be idle before the
timer expires, the transmitter may start transmitting a preamble in
the idle channel. The preamble may include specific sequence(s)
known by the one or more receiving nodes. Embodiments also
contemplate that data transmission may start in the unlicensed
band. In one or more embodiments, control signaling may be
transmitted in the unlicensed band prior to the data. Alternatively
or additionally, embodiments also contemplate that control
signaling may be transmitted in the licensed band as described
previously.
[0135] Embodiments also contemplate that--perhaps during an access
opportunity--the one or more receiving nodes may start receiving in
the unlicensed band and may search for the preamble. A timer may
also be started to measure the time spent for searching the
preamble. Embodiments also contemplate that if the preamble is not
detected and/or the timer expires, then preamble searching may be
terminated and/or postponed until the next opportunity, for
example. Embodiments also contemplate that if the preamble is
detected, synchronization may be achieved. Then, the control
channel may be decoded to find out the properties of the incoming
transmission in the unlicensed band. The control channel may be
transmitted in the unlicensed band prior to the data transmission
or in the licensed band. The corresponding feedback, such as
ACK/NACK or channel state/quality information may be transmitted in
the licensed band, for example.
[0136] Embodiments contemplate that--as opposed to the downlink
direction where transmission originates from a single node--in the
uplink direction several WTRUs may be transmitting to a common
receiver. Embodiments contemplate techniques that may resolve the
collisions among the transmitting nodes. Embodiments contemplate
that in the uplink direction, channel access may include at least
two parts: channel sensing that may find an idle channel, and
contention resolution among the WTRUSs that may find the channel
idle at the same access opportunity.
[0137] In one or more embodiments, access opportunities for a group
of WTRUs may be non-overlapping in time to ensure that if a WTRU
may start transmission, then one or more other WTRUs may keep
silent, and in some embodiments perhaps all other WTRUs may keep
silent, until the transmission ends due to the sensing capability.
One or more embodiments may assume that WTRUs may be in each
other's sensing region. In such scenarios, either the fixed-time
sensing and/or the variable-time sensing may be used. Access
opportunities may be configured by the central controller such as
the cognitive relay node semi-statically.
[0138] Alternatively or additionally, embodiments contemplate one
or more access opportunities for a group of WTRUs that may be
overlapping in time. In one or more embodiments, several WTRUs may
find the channel idle after the performing the sensing operation
and may attempt transmission at the same time. If several WTRUs
find the channel to be available at the same access opportunity, a
contention based access scheme may be applied among the cellular
nodes. Embodiments contemplate that one or more WTRUs, and perhaps
each WTRU, may start sensing the channel as described in the
fixed-time or variable-time sensing embodiments. When the channel
becomes available, embodiments contemplate that it may be possible
that several WTRUs may find the channel available at the same time.
This may occur, for example, when the WTRUs who are sensing the
channel are affected by the same outside transmitter which could be
a WiFi node or another cellular node, for example. An example is
shown in FIG. 8. In FIG. 8, one or more embodiments may assume that
the WiFi nodes are outside the sensing regions so they (the WiFi
nodes) may transmit simultaneously. The WTRU groups 1 and 2 may
start sensing the channel at the same access opportunity.
Embodiments contemplate that if WiFi node 1 finishes its
transmission earlier, then the WTRUs in group 1 may find the
channel idle and start transmission. In such scenarios, when WiFi
node 2 may finish the transmission soon, WTRUs in group 2 may find
the channel still busy due to the transmissions of the WTRUs in
group 1. Embodiments contemplate that channel access attempts of
WTRUs in group 2 may be temporarily disabled by the central node
for power saving purposes.
[0139] Embodiments contemplate that it would be useful to resolve
the contention among the WTRUs that attempt transmission in the
same access opportunity. In one or more embodiments, contention may
occur in the initial transmission and then may be resolved by the
receiver. In some embodiments, contention may only in the initial
transmission and then may be resolved by the receiver. Embodiments
contemplate that contention resolution may be achieved by enabling
the central node to identify the transmitting WTRUs.
[0140] Embodiments contemplate that the WTRU may transmit a special
WTRU-specific pre-assigned preamble. The set of preambles may
include orthogonal sequences so that the receiver may be able to
decode the simultaneous transmissions and may identify the
transmitting WTRUs based on, at least in part, the detected
preambles. Embodiments contemplate that the once the WTRUs are
identified, scheduling grants may be sent to the identified WTRUs
in the licensed band and from that point on scheduled transmission
may take place.
[0141] Embodiments contemplate that from the time when the preamble
is transmitted to the time when the grant is received, the WTRUs
may continue transmission so that the channel may not be occupied
by another node. One or more embodiments are contemplated to manage
this transmission. Embodiments contemplate that the transmission
resources (e.g., bandwidth and/or time, etc.) may be divided into
several non-overlapping parts and this allocation may be configured
before transmission takes place in the unlicensed band. A WTRU that
finds the channel idle may randomly select one of these
non-overlapping resources and may use these resources for data
transmission until a grant may be received. In such scenarios,
embodiments contemplate that the MAC packet may also carry the WTRU
ID so that the receiver may be able to understand from which WTRU
the transmission is coming from. Embodiments contemplate that two
or more WTRUs may choose the same resource for transmission. In one
or more embodiments, the receiver may estimate the channels of
these WTRUs reliably to be able to decode the colliding
transmissions. Embodiments contemplate that orthogonal reference
signals may be used by the WTRUs and that one or more reference
signals may be configured for one or more preamble sequences (or
equivalently WTRU ID), and perhaps each preamble sequence (or
equivalently WTRU ID).
[0142] Alternatively or additionally, embodiments contemplate
that--instead of or in addition to transmitting data after the
preamble transmission and/or until a grant is received, the WTRU
may do one or more of the following: [0143] The WTRU may transmit
padding bits to keep the channel busy until a grant is received;
[0144] The WTRU may repeat the preamble until an uplink grant is
received; and/or [0145] The WTRU may get an uplink grant before the
actual transmission occurs and this uplink grant may be valid if
the WTRU finds the channel available and decides to use it. In some
embodiments, this uplink grant may only be valid if the WTRU finds
the channel available and decides to use it. In such scenarios,
this grant may be valid until a new grant is received.
[0146] Embodiments contemplate that the relay node may choose not
to assign any resources in the unlicensed band to the WTRUs, for
example if it finds that the SINR is not good enough. In such
scenarios, the WTRUs may terminate access attempt after a
predefined amount of time, or the relay node may send a message to
the identified WTRUs to postpone the transmission attempts, for
example.
[0147] Embodiments contemplate that Time-Division Duplexing (TDD)
may be used as a duplexing method for separating transmission and
reception in the unlicensed band. Embodiments recognize that when a
transmission occurs in a given direction, some kind of feedback may
be provided from the receivers. At least some feedback may be
acknowledgment and channel state/quality information. When a node
attempts to convert from reception to transmission to send feedback
to the transmitter, it may not be able to find the channel
available, perhaps resulting in a lost transmission opportunity and
increased latency. Embodiments contemplate using the licensed
channel to send feedback to the transmitting node as described
previously. Embodiments further contemplate that a node may be
receiving data in the unlicensed band and may simultaneously send
feedback to the transmitter in the licensed band. One or more
embodiments contemplate using the channel for an amount of time,
and in some embodiments perhaps a relatively long amount of time,
in a given direction. For example, the channel may be used for tens
(10s) of milliseconds for transmission in one direction.
[0148] Alternatively or additionally, embodiments also contemplate
converting from reception to transmission in an amount of time, and
in some embodiments perhaps a relatively short amount of time,
without performing sensing and starting transmission so that one or
more nodes in the vicinity will not find the channel idle and
attempt to use. In such scenarios, incumbent nodes in the vicinity
of the receiver and that are capable of sensing the transmitter may
not be affected when the receiver converts to transmission.
Referring to the exemplary illustration of FIG. 9, one or more
embodiments may assume the relay node is transmitting to the WTRUs
denoted with white (empty) circles. The WiFi nodes--shown as dark
(filled) circles--in the sensing region of the relay may keep quiet
during this transmission. Embodiments contemplate that if the WTRUs
convert to transmission mode and start transmission, these WiFi
nodes may still keep quiet because they may be in the sensing
region of the WTRUs as well. Embodiments contemplate that another
WiFi node outside the sensing region may be transmitting at the
time a WTRU starts transmission which may result in a collision of
the WTRU packet with the WiFi packet. Embodiments contemplate that
the throughput of the one or more WiFi nodes may not degrade
significantly due to these collisions if the cellular node does not
convert from transmission to reception, and in some embodiments
perhaps does not convert from transmission to reception relatively
frequently.
[0149] Embodiments contemplate that if a cellular node initiates
transmission without sensing, it may cause a collision with an
ongoing WiFi transmission. In one or more embodiments--after the
WiFi packet transmission ends--WiFi nodes may sense the channel to
be busy and may not transmit until the cellular node stops its
transmission. Also, embodiments contemplate that if the cellular
node initiates transmissions without sensing, or perhaps very
frequent transmissions without sensing, the throughput of the
incumbent system may degrade significantly due to the number of
possible collisions, which may be potentially large. On the other
hand, if the channel is used for a time after a transmission is
initiated, and perhaps a reasonably long time after a transmission
is initiated, the throughput of the incumbent system may degrade
slightly because perhaps one packet may be lost over a long
interval, for example.
[0150] Embodiments contemplate one or more channel access schemes
in which a transmitter may or may not perform sensing of the
channel, and may start transmission if the channel is idle. The
channel may be used for x seconds. Embodiments also contemplate
that after x seconds, the receiver may convert from reception to
transmission mode and may start transmission to the transmitter.
The transmitter may or may not perform sensing, but in one or more
embodiments the turnaround time may be short. Embodiments also
contemplate that the maximum turnaround time may be smaller than
SIFS, for example. In one or more embodiments, the channel may be
used for y seconds. Embodiments contemplate that after y seconds,
the transmitter may convert from reception to transmission mode and
may start transmission. The transmitter may or may not perform
sensing, but in one or more embodiments the turnaround time may be
short. Further, embodiments contemplate that the maximum turnaround
time may be smaller than SIFS, for example. Embodiments contemplate
that the channel may again be used for a predefined amount of time.
In one or more embodiments, this cycle may continue for a
predefined amount of time. Embodiments also contemplate that one or
more nodes, and in some embodiments perhaps all nodes, may keep
quiet until a new cycle of transmission starts. In one or more
embodiments, the previously described transmission durations (x, y,
and any other predefined duration) may be relatively large as
compared to the maximum packet length of the incumbent system, for
example.
[0151] Embodiments contemplate that the duration of the sensing may
be a consideration in maximizing the probability that LTE nodes may
successfully access the unlicensed spectrum, while perhaps avoiding
interrupting ongoing transmissions in incumbent systems.
Considering the prevalent WiFi networks, WiFi networks may be
treated as perhaps the most numerous incumbent systems in one or
more embodiments. The 802.11 standards define different waiting
time, SIFS, PIFS, DIFS, etc., for nodes to access the channel.
Embodiments recognize that the relationship between these three
durations may be: Short Interframe Space (SIFS)<Point
Coordination Function (PCF) Interframe Space (PIFS)<Distributed
Coordination Function (DCF) Interframe Space (DIFS). WiFi nodes may
determine that the channel is idle for DIFS duration before
launching any transmissions. WiFi nodes may wait for an idle period
of SIFS time between DATA frames and ACK frames. Embodiments
recognize that PIFS may be used in a point coordination function
(PCF) of 802.11. Though specified in 802.11 standards, embodiments
recognize that PCF is not adopted by WiFi alliance and thus may not
be implemented in current WiFi nodes. As a result, few if any WiFi
devices may use PIFS in channel access.
[0152] Embodiments contemplate that LTE nodes may sense the
spectrum for PIFS duration, which may ensure that the LTE nodes may
not interrupt ongoing WiFi transmissions, while helping to
establish that LTE may have higher priority in accessing the
channel than WiFi nodes. When LTE and WiFi nodes may start sensing
the channel at the same time, LTE nodes may start transmission in
PIFS time, which may cause the channel to be busy and thus WiFi
nodes may defer their transmissions. Embodiments contemplate that
sensing duration may refer to the total time spent for the sensing
of the channel by the PHY layer, propagation delay, MAC processing
delay, RX/TX turnaround time, and/or other operations. Embodiments
contemplate that if the physical sensing is continuous, the
duration may be larger than SIFS and may be smaller than DIFS. If
the physical sensing is discontinuous, then the duration from the
starting of the first sensing period to the end of the last sensing
period may be larger than SIFS and smaller than DIFS. This may help
ensure that the channel is not accessed in the time after a data
packet may be transmitted by a WiFi node and when an ACK packet may
be expected. An exemplary timing is illustrated in FIG. 10. An
acknowledgement (ACK) packet may be transmitted by the WiFi device
after a data packet is received. In one or more embodiments, the
interval between the data packet being received and the ACK is
transmitted may be equal to the SIFS.
[0153] The channel utilization rate (e.g., a percentage of time the
channel may be busy) of incumbent non-LTE systems may be a factor
in LTE node access in the unlicensed spectrum. Embodiments
contemplate that LTE systems may adjust its spectrum usage
according to the channel utilization rate of incumbent non-LTE
systems, perhaps in order to ensure high performance for LTE and
perhaps avoid severely degrading the performance of non-LTE
systems. Embodiments recognize that the channel utilization rate of
incumbent non-LTE systems may be different at different locations,
and thus different values, and perhaps significant values, may be
observed by different WTRUs. In addition, there may be a limited
number of unlicensed spectrum channels that LTE systems can access.
Embodiments further recognize that the channel utilization rate of
incumbent non-LTE systems in each channel may be different.
Embodiments contemplate that it may be useful to collect the
channel utilization rate of incumbent non-LTE systems observed by
one or more WTRUs, and perhaps each WTRU, as part of its
measurements and coordinate the transmissions from and to the WTRUs
based on the collected data.
[0154] Embodiments contemplate one or more techniques for
transmissions in LTE cellular networks with infrastructure relays.
In one or more embodiments, the relay may monitor the transmission
queue length (or buffer status report) of each WTRU, based on which
it may determine whether the backlog for a WTRU may be too much and
thus extra bandwidth in the unlicensed spectrum may be needed for
this WTRU. This information can also be used to determine load on
an unlicensed band. If extra bandwidth is needed, the relay may
then determine the desired usage in the unlicensed spectrum.
Embodiments also contemplate that the relay may send a channel
sensing request to some or all WTRUs that may need extra bandwidth
in the unlicensed spectrum. One or more embodiments recognize that
if the relay has historical data collected for a WTRU, and/or the
WTRU may not be moving fast, the relay can make use of the
historical data and channel sensing for this WTRU. This may reduce
channel sensing time.
[0155] Embodiments contemplate that upon reception of a channel
sensing request, a WTRU may sense the channel for a pre-defined
sensing period (which for example may be in the order 10 ms or 100
ms), in order to obtain the channel utilization rate of the
incumbent non-LTE systems in several channels of the unlicensed
spectrum. The WTRU may then report to the relay K channels that may
be associated with the lowest channel utilization rate of incumbent
non-LTE systems. Embodiments recognize that a WTRU can make use of
historical sensing results to estimate which channels are mostly
likely to be in low usage, and sense those channels first, for
example. This may reduce channel sensing time. In addition to the
WTRUs, relays and other cellular nodes that may intend to operate
in the unlicensed spectrum may also perform similar
measurements.
[0156] Embodiments also contemplate that a relay may assign
different channel access attempt slots to different WTRUs,
according to their respective desired usage in the unlicensed
spectrum and/or the channel utilization rate of the incumbent
non-LTE systems in different channels. More specifically, one or
more embodiments contemplate that different WTRUs may be assigned
to different channels, and in some embodiments may be assigned to
different channels whenever possible. Embodiments also contemplate
that if assigned to the same channels, different WTRUs may attempt
to access the channel at different time slots, so that there may be
fewer, if any, collisions and in some embodiments perhaps no
collisions. Embodiments contemplate that should a channel
utilization rate of one or more incumbent non-LTE systems in the
channel assigned to a WTRU be x percent, then the usage of the WTRU
in the unlicensed spectrum may be less than (100-x) percent in
order not to reduce the data rate of the incumbent system, for
example. Embodiments also contemplate that WTRUs that may require
higher usage in the unlicensed spectrum may be assigned more
attempt slots for a given time period.
[0157] One or more contemplated embodiments may resolve collisions
when there may be independent links of unlicensed usage among
several nodes in close proximity. As illustrated in FIG. 11 where
the cellular nodes communicating with each other (for example as in
client communications networks) are indicated by the clear (empty)
circles, the central controller is indicated as a black (filled)
box, and the incumbent nodes are indicated as dark (filled)
circles.
[0158] Embodiments contemplate that sensing the activity of
non-cellular nodes before accessing a channel in the unlicensed
spectrum may minimize the disruption on the incumbent
communications. Because incumbent nodes, such as local area network
nodes, may start and end their transmissions dynamically,
measurements related to this activity may not be shared very
promptly. Embodiments contemplate that long term statistics about
channel activity may be measured and fed back to the central
controller for processing. One or more embodiments contemplate that
nodes may measure the level of interference due to non-cellular
nodes and perhaps the statistics about the interference, for
example how often it occurs, maximum interference level, etc. These
measurements may carry information about whether there are
incumbent networks in the vicinity, the activity level of these
networks if any, and/or the expected interference from these
networks. Embodiments contemplate that, based at least in part on
these measurements, the central controller may configure certain
channel access parameters and/or interference control/avoidance
parameters such as maximum transmit power, which channels of the
unlicensed band to use, among others, for example.
[0159] Embodiments contemplate that, depending at least in part on
the measurements, the network may configure the usage of the
unlicensed band semi-statically. One or more embodiments
contemplate that if the activity level or interference in one
channel of the unlicensed band may be too large and/or there may
not enough idle channel opportunities, the network may stop using
that channel until the conditions improve, or start using the
channel at all times (perhaps without sensing) but with a
modulation and coding scheme (MCS), and in one or more embodiments
perhaps a conservative MCS. Embodiments contemplate that a
conservative MCS may include that a lower modulation order and
higher coding rate may be used, which may result in a lower data
rate. In such scenarios, the channel may be treated as a regular
component carrier with low SINR.
[0160] Embodiments recognize that the Federal Communications
Commission (FCC) originally conceived the license-exempt bands to
provide a no-cost portion of public access spectrum with two
provisions. First, the transmitter could cause no harmful
interference to any nearby licensed services, and secondly, any
receiver in this band must be able to accept any interference that
may be present.
[0161] FCC regulations require that transmitters in unlicensed band
may not cause harmful interference to others. Embodiments recognize
that it is also potentially injurious to incumbent unlicensed band
users (e.g., WiFi) if an LTE system may be too demanding in
accessing unlicensed band. Therefore, the impact to incumbent
unlicensed band users may be examined when an LTE system accesses
the unlicensed band. In one or more embodiments, it may be assumed
that an LTE system co-exists with an 802.11g WLAN in the same band.
The impact of the LTE channel access fixed-time sensing
embodiments, continuous sensing embodiments, and no sensing are
examined. Also, for the purpose of comparison, a scheme where LTE
node accesses the channel exactly like WiFi nodes is examined. For
purpose of exemplary illustration, there are ten WiFi users in the
WLAN. Under such setup, simulations results for co-existed LTE/WiFi
networks have been obtained.
[0162] In simulations for reference access schemes that may be like
WiFi, the performance of the contemplate embodiments is compared
with that of a WiFi access scheme. Stated somewhat differently,
scenarios in which LTE nodes may access the unlicensed spectrum in
much the same fashion as WiFi does, and perhaps exactly as WiFi
does, and such performance is compared with that of the
contemplated embodiments.
[0163] As shown in FIG. 12, one or more contemplated embodiments
may assume that LTE nodes may be exactly like WiFi nodes. For
example, LTE nodes may understand WiFi packets, set NAV, wait for
DIFS before transmissions, do backoff, etc. By adjusting LTE
transmission duration, LTE system can get different fraction of
time that LTE system occupies the unlicensed spectrum, as shown in
the example of FIG. 13.
[0164] As described previously, one or more embodiments contemplate
LTE access schemes that may employ fixed-time sensing. As shown in
FIG. 14, there are at least two useful parameters in the
contemplated fixed-time sensing schemes--LTE transmission duration
and LTE attempt interval. By adjusting these two parameters, LTE
systems can get a different fraction of time that an LTE system may
occupy the unlicensed spectrum, as shown in FIG. 15.
[0165] As described previously, one or more embodiments contemplate
LTE access schemes that may employ variable-time (or continuous)
sensing. As shown in FIG. 16, there are at least two useful
parameters in the contemplated continuous sensing schemes--LTE
transmission duration and LTE attempt interval. By adjusting these
two parameters, LTE systems can get a different fraction of time
that an LTE system may occupy the unlicensed spectrum, as shown in
FIG. 17. In FIG. 17, the LTE attempt interval is set to 50 ms; for
other LTE attempt intervals, very similar results are observed (but
not shown).
[0166] As described previously, one or more embodiments contemplate
LTE access schemes in which no sensing may be performed. As shown
in FIG. 18, there are two important parameters in the proposed "no
sensing" schemes--LTE transmission duration and LTE attempt
interval. By adjusting these two parameters, LTE system can get
different fraction of time that LTE system occupies the unlicensed
spectrum as shown in FIG. 18. In FIG. 18, embodiments contemplate
that the transmitter may start transmission and then may wait for a
specific amount of time, perhaps a predetermined amount of time,
until starting again. One or more such embodiments may be referred
to as on/off schemes.
[0167] Embodiments contemplate that by adjusting LTE transmission
duration, LTE systems may also manage the interference level (SIR)
in the presence of LTE/WiFi collisions. The maximum transmission
time in WiFi systems may be fixed and may be determined by the
lowest WiFi transmission rate and maximum packet length. If LTE
transmission time is longer than WiFi maximum transmission time,
LTE/WiFi collisions may occur, and in some embodiments may only
occur, in the front portion of an LTE transmission, but may not
occur in the other portions of an LTE transmission. This is because
if WiFi transmission duration may be shorter than an LTE
transmission duration, some or all WiFi nodes may find the channel
busy after the WiFi transmission ends, so few if any WiFi nodes may
start a new transmissions duration the rest LTE transmission time.
Therefore, a longer transmission time may be preferable for an LTE
node, since a smaller portion of LTE transmissions may be at the
risk of collisions.
[0168] From simulation results illustrated in FIG. 20A, FIG. 20B,
and FIG. 20C, it may be observed that when WiFi load is heavy, WiFi
throughput may, and in some instances may always, drop if LTE
system uses the same unlicensed spectrum. In the case of median
WiFi load, the LTE system can occupy the spectrum for up to about
50% of the time, for example, without degrading WiFi performance.
In the case of light WiFi load, the LTE system can occupy the
spectrum for up to about 80% of the time, for example, without
degrading WiFi performance. Therefore, embodiments contemplate that
an LTE system may find (or determine) the fraction of time that the
unlicensed spectrum is occupied by non-LTE devices. If the channel
is used for x percent of the time by incumbent systems, then LTE
can, and in some instances can at most, use the channel for (100-x)
percent of the time without degrading WiFi throughput, for example.
This also suggests that the fraction of channel time occupied by
the incumbent systems may be a useful parameter in LTE channel
access schemes for unlicensed spectrum for one or more of the
contemplated embodiments.
[0169] In view of the embodiments described herein, and referring
to FIG. 21, embodiments contemplate a wireless transmit/receive
(WTRU) device that may be configured, at least in part, to
establish communication. The WTRU configuration may comprise, at
2102, sending a signal to a physical (PHY) layer from at least one
higher layer, and at 2104, selecting a first access opportunity for
a first channel in a first frequency band in response to the
signal. Embodiments also contemplate at 2106, the WTRU
configuration may include determining a state of the first channel,
and at 2108, may include determining a second channel in a second
frequency band upon a determination that the state of the first
channel is idle. At 2110, the WTRU configuration may include
sending a signal to a recipient device via the second channel.
Embodiments contemplate that the signal may include information for
reception via the first channel of data corresponding to the
information.
[0170] Embodiments contemplate that the first frequency band may be
at least one of an unlicensed band or a lightly-licensed band, and
that the second frequency band may be a licensed band, for example.
Embodiments also contemplate that the at least one higher layer may
be a medium access control (MAC) layer. Also, embodiments
contemplate that the determining the state of the first channel may
further include, at 2112, sensing the first channel at the first
access opportunity. Embodiments contemplate, at 2114, that the
configuration may further comprise waiting for a second access
opportunity upon determining that the state of the first channel is
busy. Embodiments contemplate that the second access opportunity
may be separated in time from the first opportunity by an integer
multiple of a fixed interval.
[0171] Embodiments further contemplate that, at 2116, the
configuration of the WTRU may further comprise transmitting bits
via the first channel upon determining that the state of the first
channel is idle. Embodiments contemplate that the transmitted bits
may include at least one of random bits or a preamble that may be
known to the recipient device. Embodiments contemplate that, at
2118, the WTRU configuration may further comprise transmitting via
the first channel the data corresponding to the information to the
recipient device. Also, embodiments contemplate that the second
channel may be a control channel.
[0172] Alternatively or additionally, and referring to FIG. 21A,
embodiments contemplate, at 2120 that the configuration may further
comprise starting a timer upon the selection of the first access
opportunity. Embodiments contemplate, at 2122, that the WTRU
configuration may further comprise waiting for a second access
opportunity upon determining that the state of the first channel is
busy and an expiration of the timer. Embodiments also contemplate,
at 2124, the WTRU configuration may further include transmitting
bits via the first channel upon determining that the state of the
first channel is idle prior to an expiration of the timer.
Embodiments contemplate that the transmitted bits may include at
least one of random bits or a preamble known to the recipient
device, for example.
[0173] Referring to FIG. 22, alternately or additionally,
embodiments contemplate a wireless transmit/receive device (WTRU)
that may be configured to establish communication. At 2202, the
WTRU configuration may include sending a signal to a physical (PHY)
layer from at least one higher layer, and at 2204, selecting a
first access opportunity for a first channel in a first frequency
band in response to the signal. Embodiments contemplate that, at
2206, the configuration may include determining a state of the
first channel, and at 2208, determining a second channel in the
first frequency band upon a determination that the state of the
first channel is idle. Embodiments contemplate that, at 2210, the
WTRU configuration may include sending a signal to a recipient
device via the second channel. The signal may include information
for reception via the first channel of data corresponding to the
information. Embodiments also contemplate that the first frequency
band may be at least one of an unlicensed band or a
lightly-licensed band.
[0174] Embodiments contemplate, at 2212, that the WTRU
configuration may further comprise transmitting a preamble via the
first channel upon determining that the state of the first channel
is idle. At 2214, the WTRU configuration may further comprise
transmitting via the first channel the data corresponding to the
information to the recipient device. Embodiments contemplate that
the second channel may be a control channel. Embodiments further
contemplate that the preamble may include a sequence known to the
recipient device and that the sequence may enable synchronization
with the recipient device.
[0175] Referring to FIG. 23, alternatively or additionally,
embodiments contemplate a wireless transmit/receive device (WTRU)
that may be configured to establish communication. Embodiments
contemplate that, at 2302, the WTRU configuration may include
detecting a first access opportunity for a first frequency band. At
2304, the WTRU configuration may include monitoring for a preamble
in the first access opportunity. At 2306, the WTRU configuration
may include starting a timer upon the detection of the first access
opportunity. At 2308, the WTRU configuration may include
synchronizing with a transmitting device upon a detection of the
preamble. At 2310, the WTRU configuration may include decoding a
control channel in the first frequency band upon the detection of
the preamble. Embodiments contemplate that the first frequency band
may be at least one of an unlicensed band or a lightly-licensed
band.
[0176] Embodiments further contemplate that, at 2312, the WTRU
configuration may comprise detecting a second access opportunity
for the first frequency band upon the detection of the preamble not
occurring prior to an expiration of the timer. At, 2314, the
configuration may further comprise transmitting feedback to a
transmitting device via a second frequency band. Embodiments
contemplate that the second frequency band may be a licensed
band.
[0177] Although features and elements are described above in
particular combinations, one of ordinary skill in the art will
appreciate that each feature or element can be used alone or in any
combination with the other features and elements. In addition, the
methods described herein may be implemented in a computer program,
software, or firmware incorporated in a computer-readable medium
for execution by a computer or processor. Examples of
computer-readable media include electronic signals (transmitted
over wired or wireless connections) and computer-readable storage
media. Examples of computer-readable storage media include, but are
not limited to, a read only memory (ROM), a random access memory
(RAM), a register, cache memory, semiconductor memory devices,
magnetic media such as internal hard disks and removable disks,
magneto-optical media, and optical media such as CD-ROM disks, and
digital versatile disks (DVDs). A processor in association with
software may be used to implement a radio frequency transceiver for
use in a WTRU, UE, terminal, base station, RNC, or any host
computer.
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